The cambium is rapidly broken down, and the stele is invaded through the avenues of least resistance. Many such depressions are found on the roots, so that it is evident why the death of an alfalfa or cotton plant under optimum conditions for the disease is effected within a week. Finally the stele elements are broken down and disorganized, and upon the invaded tissues the mycelium, which serves as a reserve for the strand hyphæ, grows profusely. The polymorphic nature of Ozonium, together with its unusual method of entrance and its subsequent behavior within the tissues, makes it an extremely interesting subject for extended investigations. (1) DUGGAR, B. M. LITERATURE CITED 1916. THE TEXAS ROOTROT FUNGUS AND ITS CONIDIAL STAGE. Ann. Mo. Bot. Gard., vol. 3, p. 11-23, illus. (2) DURAND, E. J. 1911. THE DIFFERENTIAL STAINING OF INTERCELLULAR MYCELIUM. Phytopathology, vol. 1, p. 129-130. (3) KING, C. J. (4) 1923. COTTON BOOTROT IN ARIZONA. Jour. Agr. Research, vol. 23, p. 525527. 1924. HABITS OF THE COTTON ROOTROT FUNGUS. Jour. Agr. Research, vol. 26, p. 405-418, illus. (5) SCOFIELD, C. S. 1919. COTTON ROOTROT SPOTS. (6) SHEAR, C. L. Jour. Agr. Research, vol. 18, p. 305-310, 1907. NEW SPECIES OF FUNGI. Bul. Torrey Bot. Club, vol. 34, p. 305-317. (7) 1925. THE LIFE HISTORY OF THE TEXAS ROOT-ROT FUNGUS, OZONIUM OMNIVORUM SHEAR. Jour. Agr. Research, vol. 30, p. 475-477, illus (8) TAUBENHAUS, J. J., and KILLOUGH, D. T. 1923. TEXAS ROOTROT OF COTTON AND METHODS OF ITS CONTROL. Tex. Agi Exp. Sta. Bul. 307, 98 p., illus. (9) VAUGHAN, R. E. 1914. A METHOD FOR THE DIFFERENTIAL STAINING OF FUNGOUS AND HOST CELLS. Ann. Mo. Bot. Gard., vol. 1, p. 241–242. 27 UNITED STATES DEPARTMENT OF AGRICULTO BE August 9, 1926 Secretary of Agriculture. Director of Scientific Work_ Director of Personnel and Business Admin istration-- Solicitor__ Weather Bureau__. Bureau of Agricultural Economics Bureau of Animal Industry. Forest Service - Bureau of Chemistry. Bureau of Soils. Bureau of Entomology. Bureau of Biological Survey_-. Bureau of Public Roads .... Fixed Nitrogen Research Laboratory---- Federal Horticultural Board_. Packers and Stockyards Administration_-_- W. M. JARDINE. R. W. DUNLAP, WALTER G. CAMPBELL. C. W. WARBURTON. NELSON ANTRIM CRAWFORD. W. W. STOCKBERGER. R. W. WILLIAMS. CHARLES F. MARVIN, Chief. C. A. BROWNE, Chief. L. O. HOWARD, Chief. E. W. NELSON, Chief. THOMAS H. MACDONALD, Chief. LOUISE STANLEY, Chief. C. W. LARSON, Chief. F. G. COTTRELL, Director. E. W. ALLEN, Chief. C. B. SMITH, Chief. This bulletin is a contribution from Bureau of Plant Industry-‒‒‒ 28 WILLIAM A. Taylor, Chief. O. F. Cook, Senior Botanist, in Charge. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM AT 15 CENTS PER COPY UNITED STATES DEPARTMENT OF AGRICULTURE DEPARTMENT BULLETIN No. 1418 Washington, D. C. July, 1926 FERTILIZER EXPERIMENTS WITH ALFALFA CONDUCTED AT THE UNITED STATES YUMA FIELD STATION, BARD, CALIF., 1919 TO 1925 By H. L. WESTOVER, Agronomist, Office of Forage Crops, and EDWARD G. NOBLE, Farm Superintendent, Office of Western Irrigation Agriculture, Bureau of Plant Industry The agriculture of the Yuma Reclamation Project has been built up largely around the alfalfa-hay and alfalfa-seed industries. From the beginning these crops have constituted and to a large extent still represent the real backbone of the farming operations. Naturally, when the yields began to decline a few years ago the farmers became much concerned. This led to the need of experimental work to assist in arriving at some satisfactory explanation for the decreasing yields. With this in mind, some rather simple fertilizer experiments were begun in 1919 at the United States Yuma Field Station, Bard, Calif., the results of which indicated the efficiency of available phosphoric acid. Further tests have shown pretty conclusively that phosphoric acid when applied in the form of acid phosphate increases the alfalfa yields sufficiently to render its use very profitable. Some of the details of these tests are presented in the following pages. HISTORICAL AND STATISTICAL DATA The agricultural area of the Yuma Reclamation Project comprises about 110,000 acres lying on both sides of the Colorado River in California and Arizona and situated just north of the Mexican line. About 65,000 acres of this land lies in the valley, and before the construction of levees was subject to overflow. The valley soils are alluvial in origin and range in texture from almost pure sand to heavy clay. Except where they are highly impregnated with alkali or else very sandy, the soils in general have been very productive. Farming was begun in the Yuma Valley about 1890. The early agriculture was confined to the production of grain and alfalfa. 93186°-26 |